1. Field of the Invention
The present invention relates to a noise rejection device for removing high frequency noise from a signal line or the like and a cellular phone including the noise rejection device.
2. Description of the Related Art
An increase in signal processing speed has been advanced in digital equipment such as a cellular phone and a personal computer in accordance with enhancement of functions of the digital equipment. There are many types of digital equipment that use a CPU having a clock frequency exceeding 1 GHz. In a digital circuit having a clock frequency exceeding several hundred MHz, high frequency noise is generated not only in a band of a harmonic thereof but also in a GHz band where a higher harmonic appears. Thus, it is necessary to remove high frequency noise in a broad band of several hundred MHz to several GHz. It is also demanded to control dumping of waveforms by maintaining impedance on a low frequency side. Usually, multiple components such as beads and resistors are used to cope with this problem. Thus, a reduction of the number of components is demanded.
A bead type inductor element, in which a coil conductor is arranged in a magnetic core, is generally used as a device for removing high frequency noise. The device of this type has an impedance peak only in a specific frequency band far higher than those in other frequency bands. Thus, plural devices having impedance peaks different from one another have to be used concurrently in order to remove high frequency noise in the broad band of several hundred MHz to several GHz. As a result, cost for designing circuits increases (see, for example, JP-A-2000-156622).